Sensitive drill press



' zsmwz w. M. DAVIS SENSITIVE DRILL PRESS March 19, 1946;

2 Sheets-Sheet 1 Filed Feb. 26, 1943 WMMM b arch 19, w DAVHS I SENSITIVE DRILL PRESS Fil ed Feb. 26, 194s 2 Sheets-Sheet 2 Patented Mar. 19, 1946 UN IT ED STATES PATENT OFFICE 1claim.

This invention relates to improvements-in drill presses-such as are used for drillingtiny holes through sheet metal. For example, such holes must be drilled in circular plates which are used in watches to support the arbors for the gearsin the works. Likewise, the holes drilled in spinnerets for the extrusion'of viscose, etc., are very fine. Since the holes to be drilled are of small diameter, the drills themselves must be of equally small diameter and are therefore liabl'eto break unless'manipulated with great care. For drilling of this type drill presses are used wherein'the drill is manuall pressed against the work. Breakage of the drill is most apt to occur just after the tip of the drill' has penetrated through the bottom of the plate which is being drilled. Hence it is important to reduce the pressure on the drill-at this point in the operation.

It is an object of the present-invention toprovide a drill press in which the drill isso supported that the slightest variation in resistance to-the axial progress of the drill is easily felt. The'opventiOn, reference may behad to the-following de- 35 scription thereof, and to the drawing-sot which Figure 1 is a side elevation of a machine embodying the invention.

Figure 2 is a rear elevation of the same.

Figur 3 is a side elevation of the drilling head 40 shown in Figure 1, portions being broken away to show in section. 7

Figure l is a section on the line 4-- 4 of FigureS.

Figure 5 is a section on'theline 5--5 of Figure 3, drawn on a greatlyenlargedscale. I

Figured is a section on the line 6-6 of Figure'l.

- Figure '7 is similar to Figure 6 but shows a portion of. a multiple spindle machine.

Figure 8 isasection on the line 8 8-of Figure fl.

Figure 9 isa section on the line 9-9-of Figure2. 50

Figure l0 isa fragmentary elevationof-an end bearing of the countershaft, showing-how the belt isto-be mounted.

Figure-ll-isa section on the line I IH 'of'Figure -10.

Thus th spindle responds to The mechanism illustratedi-n Figure i prefer-- ably includes a suitable base -25 above-which ;-a Work-table 2-2 is supported bya pair of standards 24. A- bracket 26' is secured to therear edge of the work-table 22, preferably by a lu'g 28-which fits into'a T-slot in the rear edge-of" the table and is secured therein by a suitable bolt (not shown). The T-slot extension extends the en'- tire length of th'e'table 2-2 and can'accemmodate'= two or more brackets 26 according to-the -l'eng th of thetable 22 the number of'drillin'g headsdesired. One drilling head is illustrate'cl in Figsure 1 butmoremaybeemployed as hereinafter described.

Adjustably secured in the bracket 26 is a verti cal pil1ar'30 to which is'secured' a drilling head 32. The drilling head is provided with two vertically' spaced and alined bearings 34 and 36 each of which is preferably equipped with suitable needle bearings such as are illustrated in Figure 5. Each such bearing consists of a tubular bearing race 38 in which a series of needle-like bear ing elements 40 roll freely. Bearings of thisdescripti'on are well known in the art. A 'drillspin- 5 dle 42 is freely rotatable in these bearings and is also axially slidable therein. During rotation of' the spindle 42 the frictional opposition to axial movement of the spindle in either direction ispractically zero. At the lower end of the spindle 42 is mounted asuitable drill chuck 44 which may be of any'desired description. The upper end 46 of the spindle is supported in a bearing member 48 within which it rotates freely. Aplain bearing. member is illustrated in Figure 3 but a ball hearing may be employed .at thi point. The needle bearingsdfl are suitably lubricated by any desired means such as oil cups 5G; The spindle assembly, including the spindle 42 and the drill chuck 44, is

adapted to be depressed toward work on the table 22 by manually operable means such as is illustrated in Figure 1. This mean comprises a lever 52 pivoted at the point 54, the pivot being supported by an arm 56 which projects rearwardly from the bracket 26. On the forward end of the lever 52 isa suitable finger-button 58 which is conveniently placed for operation. At an intermediate point of the lever 52 a vertical rod 62 is pivotally connected by a pivot 60. This rod may pass up through the interior of the pillar 30 which is preferably hollow for this purpose. The upper end of the rod 62 is pivotally connected at '64 to a horizontal arm (i6 which rocks about a fixed pivot point 68, this pivot being on a bracket 10 which extends to the rear of the drilling-head 32.

In order to'counterbalance-in part the downward pull of gravity on the lever arm 52 and the rod 62, a suitable compression spring I2 is provided as indicated in Figure 3 to encircle the upper portion of the rod 62 and press upwardly against the fitting at the upper end thereof. It is preferred that only 85% to 90% of the gravitational force acting on these parts be carried by the spring 12 during the operation of the mechanism. The forward end I4 of the arm 66 thus bears on the bearing member 48 at the top of the spindle 42.

Since the pillar 30 is adjustable rotatably in the bracket 26, the pillar and the entire drilling head may be adjustably swung around the axis of the pillar, but, when the mechanism is in use, the bracket is set up tightly-to grip the pillar and hold it fixed. In somewhat similar manner the arm 56 is independently adjustable about the axis of the pillar 30 so that the finger-button 58, which is handily located just below the forward edge of the work table, can be shifted laterally to the position most convenient to the operator and secured in such position.

Fixed on the spindle 42 is a grooved belt pulley I6 which, as indicated in'Figures 1 and 3, maybe a double pulley having two different diameters so that the spindle may be driven at different speeds by a driving belt 80. The pulley I6 is preferably mounted on thespindle 42 between the bearings 34 and 36 so that these bearings act as limit stops to the vertical axial movement of the pulley I6 and consequently of the spindle assembly of which the pulley is a part.

In order further to counterbalance the gravitational pull on the spindle assembly and also a portion of the gravitational pull on the depressing mechanism which includes the arms 52 and 66, the driving belt 80 and guide pulleys 84 and 86 therefor are so arranged that one or both of the stretches of the belt which lead from the drive pulley 1B are inclined upwardly so that the upward component of the tension on the belt acting on the upper flange of the pulley which confines the belt in the groove of the pulley, applies a counter force opposing the. gravitational forces her'einbefore mentioned. In the embodiment f theinvention illustrated in Figure 1, one such stretch of the belt 39 is upwardly inclined, the stretch which travels toward pulley I6 being sub stantially horizontal so that the belt will more certainly remain on the pulley during the operation of the mechanism. By delicate adjustment of the belt tension, as hereinafter described, the spindle assembly can be made to float with the pulley I6 at any desired level between the bearings 34; In actual operation it is preferable to support the pulley 15 near the upper bearing 34. Since frictional opposition to axial movement of the spindle assembly during rotation thereof is virtually eliminated, the mechanism is very sensitive to any downward pressure on the fingerbutton 58. Hence, the slightest change in resistance to the progress of th drill in the work is easily felt by the operator so that the drillcan be accurately controlled to minimise breakage. A semi-cylindrical guardor shield 82 may be'provided in front of the pulley and the portion of the spindle between the two bearings.

The belt 39, as indicated in Figure 1, may pass over two idler pulleys 84 and 86 and around a double pulley 88 which is mounted on a suitable countershaft 98. This oountershaft may be conveniently journaled in bearing-members 92 (FigureslO and ll) which are supported by suitable brackets 94. These brackets, as indicated in Figures 6 and 8, may be clamped against a pair of horizontal rods 96 and 98 either by an angle piece I00 or by a clamping member I02. This permits lateral adjustment of the brackets 94. Also mounted on the countershaft 90 is a double pulley I04 connected by a belt I06 to a pulley I08 mounted on the shaft H0 of a suitable electric motor II2 mounted on the base 20. The double pulleys 88 and I04 are each provided with two sheaves of difierent diameters for the purpose of driving the spindle 42 at different speeds. By selecting different combinations of the pulleys I6, 88 and I04, a considerable variety of speeds of rotation of the spindle 42 can readily be had.

The idler pulleys 84 and 86 are carried by a standard I20 which is pivotally mounted on the rod 96. By adjustably tilting the standard I20, the tension on the belt can be readily adjusted as is evident from Figure 1. The means for adjusting the position of the standard I20 is illustrated'in Figure 9. As shown, a lever I22 is pivotally mounted as at I24 on the lower end of the standard I20 which is below the rod 96. The upper end portion I26 of the lever I22 rests against an eccentric collar I28 which is rotatable on the rod 96. The lower end I30 of the lever I22 rests against the rod 93. The eccentric collar I28 is normally secured against rotation by a setscrew I32 which presses against the rod 96 to bind the collar I28 in adjusted position. The setscrew I32 can be backed ofi by manipulation of the head of the screw which is then used as a handle to rotate the collar I28 about the rod 96. .This rotation results in a slight rocking movement of the lever I22 which in turn results in a slight rocking movement of'the standard I20 about the rod 96 as a pivot. In this manner, a very delicate adjustment of the belt tension can easily be had. In order to maintain a constant tension on the belt 80 in spite of possible stretching or other changes in the belt, the idler pulley 86 is carried by an arm I34 which is pivoted to the standard I20 as at I36. Acoiled spring I38 is employed to press the arm I34 resiliently in a clockwise direction as illustrated in Figure l, a suitable stop (not shown) being provided to limit such movement of the arm I34. The strength of the spring I38 is preferably such that normal tension on the belt 80 will swing the arm I34 a small amount in a counterclockwise direction away from the stop. This results in a resilient slack take-up device which helps to maintain the spindle assembly at a constant level when the finger-button 58 is not touched.

In order to avoid vibration in the apparatus when operated at high speeds, it is preferable to employ an endless belt. In order to be able to mount and dismount such a belt without disassembling the countershaft assembly, the bearing members 92 are made in the form of circular disks each having a notch I40 which can be moved into registry with a notch I42 in the bracket 94 in which the bearing member 92 is supported. A shallow peripheral groove I44 is also provided in the'bearing member 92 in order to accommodatea binding screw I46 which is employed to set up the split end of the bracket 94 in order to pinchthe bearing member 92 firmly in position. Figure 11 shows a plain bearing member 92 but in practice a ball bearing or roller bearing may be employed to advantage. When the screw I46 is released, the bearing member 92 may be rotated to bring the notch I40 into registry with the notch I42 as indicated in Figure 10. A loop of the belt 80 may then be thrust through the opening made by the notches I40 and I42. When the belt is in the position shown in Figure 10, the bearing member 92 is rotated once to carry a portion of the belt around the countershaft. The remainder of the belt is then pulled through the notch, whereupon the belt is ready to be extended around the adjacent pulley 88 and over the idler pulleys 84 and 86 to the spindle pulley 16.

Figure '7 illustrates the rear portion of the mechanism when provided with two spindle assemblies and driving belts for the same. By employing a longer countershaft 90 and, if desirable, longer rods 96 and 98, additional drill units may be carried by the boss 20, each such unit including a drill spindle assembly with a pillar 30 and a depressing means as illustrated in Figure 1, a standard I20 to support a pair of idler pulleys, and a driving pulley 88 mounted on the shaft 90.

It is evident that various modifications and changes may be made in the embodiments of the invention herein shown and described without departing from the spirit or scope thereof as defined in the following claim.

What I claim is:

A sensitive drill press comprising a base, a work table supported on and above said base, a pillar rising above the table and being mounted with provision for angular adjustment about its length dimension, a drilling head mounted on the pillar -thereto, a lever pivotally supported on said drilling head to swing in a vertical plane and coupled with said spindle for the transmission of axial movement thereto, an arm connected with the table below the supporting surface thereof with provision for angular adjustment about the same axis as the pillar, an operating lever supported pivotally by said arm to swing in a vertical plane, said arm extending under the table and near to the work supporting surface thereof and having a finger button on its free end accessible for depression by the finger of an operator, a connecting rod in pivotal connection with both said levers extendin in substantial coincidence with the axis of angular adjustment of the pillar and said arm, driving means operatively engaged with said spindle for rotating it, and a spring operatively disposed to counterbalance in large measure the gravitational force tending to move th spindle downward.

WILLIAM M. DAVIS. 

